數(shù)據(jù)刪除
數(shù)據(jù)檢索
測(cè)試代碼：
create table T_Employee
(FNumber varchar(50),FName varchar(50),FAge int,FSalary numeric(10,2)
,PRIMARY KEY(FNumber));
insert into T_Employee(FNumber,FName,FAge,FSalary)values('DEV001','Tom',25,8300);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('DEV002','Jerry',28,2300.80);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('SALES001','John',23,5000);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('SALES002','Kerry',28,'6200');
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('SALES003','Stone',22,1200);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('HR001','Jane',23,2200.88);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('HR002','Tina',25,5200.36);
insert into
T_Employee(FNumber,FName,FAge,FSalary)values('IT001','Smith',28,3900);
insert into
T_Employee(FNumber,FAge,FSalary)values('IT002',27,2800);
感興趣，可以試一試下面代碼
select FName,FAge from T_Employee
where FSalary>5000;
select FName as 姓名,FAge as 年齡 from T_Employee
where FSalary<5000;
select NEWID()
select getdate()
select 1+2
版本號(hào)：
select @@VERSION
select 1+1 as 列1,GETDATE()as 時(shí)間,NEWID() as 編號(hào);
select FName as 姓名,FAge as 年齡,FSalary+10000 as 月薪,GETDATE() as 當(dāng)前時(shí)間
from T_Employee
數(shù)據(jù)匯總
計(jì)數(shù)/最大工資/最小值/平均值/合計(jì)
select count(*)from T_Employee
select MAX(FSalary)from T_Employee
select min(FSalary)from T_Employee
select avg(FSalary)from T_Employee
select sum(FSalary)from T_Employee
檢索出工資大于5000的個(gè)數(shù)
select count(*) from T_Employee
where FSalary>5000;
數(shù)據(jù)排序
排序 升序ASC /降序DESC
select * from T_Employee
order by FSalary ASC
select * from T_Employee
Order by FSalary DESC
檢索出表，年齡升序排，工資降序排
select * form T_Employee
order by FAge DESC, FSalary ASC
當(dāng)出現(xiàn)判斷條件時(shí)，注意where關(guān)鍵字的位置
select *from T_Employee
where FAge>23
order by Fage DESC, FSalary ASC
通配符過濾（模糊匹配）
select * from T_Employee
where FName='Tom';
但是如果只有 To 字段的片段時(shí)，如何操作
單字符匹配
select * from T_Employee
where FName LIKE'_erry'
select *from T_Employee
where FName like'%n%'
select *from T_Employee
where FNumber like'DEV%';
空值處理
理解這句話null表示不知道不是沒有。
null+1=？/不知道+1=不知道
答案是null（不知道）
要想知道表中是null
select * from T_Employee
where FName is null;
不是
select * from T_Employee
where FName is not null;
多值匹配
下面的方式，作用相同或者類似，只是寫法不同取決于你高興?。。?/p>
檢索出制定的年齡
select * from T_Employee
where FAge=23,FAge=25orFAge=28;
檢索出指定的年齡
selsct *form T_Employee
where FAge in (23,25,28);
檢索出年齡在20和30之間的
select *from T_Employee
where FAge>20 and FAge <30;
檢索出年齡在23與30之間的
select *form T_Employee
where FAge between 23 and 30;
